Hydrocarbon feeds derived from various oil and gas processing operations such as, for example, various bitumen-derived hydrocarbon fractions often contain chemical species harmful to the efficient operation of downstream processes, and affect the quality of the final hydrocarbon product. Such chemical species include acidic species commonly found in hydrocarbon feeds such as, for example, various organic acids including naphthenic acids.
Acidic hydrocarbon feeds may arise, for example, when hydrocarbon feeds undergo biodegradation in situ as a result of which various acidic constituents may form, or during processing when the hydrocarbon feeds are combined with various chemical agents and processed at elevated temperatures. If the acidic constituents are allowed to remain in the hydrocarbon feed throughout the various stages of processing, they will often cause corrosion of equipment used to extract, process and transport the feed. Some species such as, for example, mercaptants and hydrogen sulfide, may cause unpleasant odour. Hydrogen sulfide is also highly toxic.
A variety of approaches have been proposed for minimizing the effects of the acidic constituents. For example, one approach involves blending of a hydrocarbon feed comprising a high naphthenic acid content with a hydrocarbon feed comprising a low naphthenic acid content. Another approach involves the use of corrosion inhibitors such as, for example, polysulfides for treating the surfaces of equipment that come in contact with the acidic hydrocarbon feed. Yet another approach involves neutralizing the acidic constituents in the hydrocarbon feed using, for example, an aqueous solution of sodium or potassium hydroxide and subsequently removing the neutralized species from the feed. Thermal and catalytic treatments have also been used to thermally crack or catalytically convert the acidic constituents into non-acidic species.
The above approaches present several difficulties especially when applied to bitumen or bitumen-derived acidic feeds. For example, in the case of neutralization of the acidic hydrocarbon feed with basic aqueous solutions, some of the undesirable effects include formation of emulsions with the hydrocarbon feed, increases in the organic salt content including those of calcium, magnesium and sodium, which further exacerbate corrosion and other issues in downstream processing. Thermal treatment approaches require high temperature and pressure, and catalytic thermal treatments often suffer from catalyst deactivation. Moreover, thermal treatment to crack and eliminate constituents may produce undesirable cracked hydrocarbon products, and depending on the complexity of the feed, thermal cracking may not be effective at reducing the content of the acidic constituents. Addition of corrosion inhibitors to the acidic hydrocarbon feed may result in other processing complications in downstream processing equipment such as catalyst poisoning, inhibition, or fouling. Approaches involving blending of various high and low TAN hydrocarbon feeds may result in high inventory costs and increased logistical and feed supply costs such as for example sourcing and obtaining delivery of lower TAN hydrocarbon feeds for blending. The use of corrosion-resistant metals in the construction of refining units results in specialized refining facilities with significant increased capital investment to provide the corrosion-resistant units. Moreover, this approach is expensive to retrofit onto existing refining facilities due to changes in component parts, increased component costs, changes in process flows and changeover production losses.
Therefore, processing acidic hydrocarbon feeds to effect a reduction in the content of the acidic constituents and to form a hydrocarbon material suitable for downstream processing operations such as, for example, upgrading remains challenging.